<template>
    <view class="sign-box">
        <image class="signImg" v-if="newValue" :src="newValue" mode="widthFix"></image>        
        <canvas class="mycanvas" canvas-id="mycanvas" @touchstart="touchstart" @touchmove="touchmove"
            @touchend="touchend" ></canvas>
        <view class="footer">
            <view class="left box-bg" @click.stop="finish">完成</view>
            <view class="right box-bg" @click.stop="clear">清除</view>
        </view>
    </view>
</template>

<script>
    var x = 20;
    var y = 20;
    // import {
    //     config
    // } from '@/utils/config.js'
    export default {
        props:{
            value:'',
            uploadFn: {
              type: Function, default: null,
            }
        },
        data() {
            return {
                ctx: '', //绘图图像
                points: [], //路径点集合
                // action: config.baseUrl + 'api/update',
                
                newValue: ''
            }
        },
        
        watch: {
            value(val, oldVal) {
                // console.log('value',val, oldVal)
                this.newValue = val;
            },
        },
        created() {
            this.ctx = uni.createCanvasContext("mycanvas", this); //创建绘图对象
            this.ctx.setFillStyle('#fff')
            //设置画笔样式
            this.ctx.lineWidth = 4;
            this.ctx.lineCap = "round"
            this.ctx.lineJoin = "round"
        },
        methods: {
            //触摸开始，获取到起点
            touchstart: function(e) {
                let startX = e.changedTouches[0].x;
                let startY = e.changedTouches[0].y;
                let startPoint = {
                    X: startX,
                    Y: startY
                };

                /* **************************************************
                    #由于uni对canvas的实现有所不同，这里需要把起点存起来
                 * **************************************************/
                this.points.push(startPoint);

                //每次触摸开始，开启新的路径
                this.ctx.beginPath();
            },

            //触摸移动，获取到路径点
            touchmove: function(e) {
                let moveX = e.changedTouches[0].x;
                let moveY = e.changedTouches[0].y;
                let movePoint = {
                    X: moveX,
                    Y: moveY
                };
                this.points.push(movePoint); //存点
                let len = this.points.length;
                if (len >= 2) {
                    this.draw(); //绘制路径
                }

            },

            // 触摸结束，将未绘制的点清空防止对后续路径产生干扰
            touchend: function() {
                this.points = [];
            },

            /* ***********************************************
            #   绘制笔迹
            #   1.为保证笔迹实时显示，必须在移动的同时绘制笔迹
            #   2.为保证笔迹连续，每次从路径集合中区两个点作为起点（moveTo）和终点(lineTo)
            #   3.将上一次的终点作为下一次绘制的起点（即清除第一个点）
            ************************************************ */
            draw: function() {
                let point1 = this.points[0]
                let point2 = this.points[1]
                this.points.shift()
                this.ctx.moveTo(point1.X, point1.Y)
                this.ctx.lineTo(point2.X, point2.Y)
                this.ctx.stroke()
                this.ctx.draw(true)
            },

            //清空画布
            clear: function() {
                let that = this;
                that.newValue = '';
                uni.getSystemInfo({
                    success: function(res) {
                        let canvasw = res.windowWidth;
                        let canvash = res.windowHeight;
                        that.ctx.setFillStyle('#fff')
                        that.ctx.clearRect(0, 0, canvasw, canvash);
                        that.ctx.draw(true);
                    },
                })
            },

            //完成绘画并保存到本地
            finish: function() {
                var that = this;                
                uni.canvasToTempFilePath({
                    canvasId: 'mycanvas',
                    success: function(res) {
                      let path = res.tempFilePath;
                      that.uploadFn && that.uploadFn(path)
                    },
                    fail: function(res) {
                        console.log(res)
                    },
                },that)
            },            
        },
    }
</script>
<style lang="scss" scoped>
.sign-box{
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  display: flex;
  flex-direction: column;
  .mycanvas,.signImg,.footer{
    width: 100%;
    height: calc(100% - 60rpx);
  }
  .signImg{
    height: 100%;
  }
  .footer{
    border-top: 1px solid #c8c9cc;
    height: 60rpx;
    display: flex;
    justify-content: space-around;
    align-items: center;
    .box-bg{
      background: #38C79D;
      color: #fff;
      padding: 0 30rpx;
      height: 40rpx;
      line-height: 40rpx;
      border-radius: 6rpx;
      &.right{
        background: #f4f4f5;
        color: #82848a;
        margin-left: 20rpx;
      }
    }
  }
}
</style>